Re: [core] draft-ietf-core-observe-05 - "obs"
Zach Shelby <zach@sensinode.com> Fri, 20 April 2012 15:38 UTC
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From: Zach Shelby <zach@sensinode.com>
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Date: Fri, 20 Apr 2012 18:38:37 +0300
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To: Klaus Hartke <hartke@tzi.org>
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Subject: Re: [core] draft-ietf-core-observe-05 - "obs"
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Hi, I would like to keep the 'obs' link attribute. From the experience deploying products and systems using CoAP so far, we have actually found this attribute useful. Two reasons: 1. Although in theory the protocol still works through trial and error as you describe below, it is useful for a CoAP client to plan its behavior before making a request. 2. Knowledge of the Observability of a resource is useful at the application layer, where some M2M application needs to make use of these resources. The behavior of dealing with a polling-only resource vs. an observable resource is pretty different, and an observable resource might result in a different graphical representation to the user which needs to be known already during discovery. I like the philosophy otherwise for finding things to take away, but not this one please. Zach On Apr 17, 2012, at 3:14 AM, Klaus Hartke wrote: > In the spirit of "In protocol design, perfection has been reached not > when there is nothing left to add, but when there is nothing left to > take away" [1]: > > Do we really need the "obs" link attribute? > > Some thoughts: > > * If a client wants to have a fresh representation of a resource over > a period of time, it can include the Observe option in its request. If > the server does not support -observe, the client can poll the resource > to achieve its goal. > > * If a client for whatever reason only wants to have a fresh > representation of a resource over a period of time if the server > supports -observe, it can include Observe option in its request and > not poll if the if the server does not support -observe. > > * If a client wants a single snapshot representation of a resource, it > can omit the Observe option from its request. > > Under what circumstances can a client not be sure if it wants to have > a fresh representation of a resource over a period of time, so a hint > from the server is needed? > > > Klaus > > > [1] http://tools.ietf.org/html/rfc1925 > _______________________________________________ > core mailing list > core@ietf.org > https://www.ietf.org/mailman/listinfo/core -- Zach Shelby, Chief Nerd, Sensinode Ltd. http://www.sensinode.com http://zachshelby.org - My blog "On the Internet of Things" http://6lowpan.net - My book "6LoWPAN: The Wireless Embedded Internet" Mobile: +358 40 7796297
- [core] draft-ietf-core-observe-05 - "obs" Klaus Hartke
- Re: [core] draft-ietf-core-observe-05 - "obs" Thomas Fossati
- Re: [core] draft-ietf-core-observe-05 - "obs" Cullen Jennings
- Re: [core] draft-ietf-core-observe-05 - "obs" Carsten Bormann
- Re: [core] draft-ietf-core-observe-05 - "obs" Zach Shelby
- Re: [core] draft-ietf-core-observe-05 - "obs" Klaus Hartke
- Re: [core] draft-ietf-core-observe-05 - "obs" Zach Shelby
- Re: [core] draft-ietf-core-observe-05 - "obs" Klaus Hartke